Single action temperature sensitive electrical switch including camming means for a plunger retaining member



Nov. 3, 1964 R F. DENTON SINGLE ACTION TEMPERATURE SENSITIVE ELECTRICALSWITCH INCLUDING CAMMING MEANS FOR A PLUNGER RETAINING MEMBER OriginalFiled June 13, 1960 3,155,800 SINGLE ACTIGN TEMPERATURE ENSiTiVEELECTRIEAL EWITQCH llNCLUEl-NG CAB/i- MENG MEANS EUR A PLUNGER RETAIN-ING MEMBER Rohert F. Denton, West Los Angel-es, Caiifi, assignor, by

Inesne assignments, to Geniseo Teehnelogy Corporation, a eerporation ofCaiiziornia Continuation of application Ser. No. 35,557, dune 13, I969.This application Jan. 2, 1963, Ser. No. 256,978 8 Claims. (Ci. 200-142)The present invention relates to a single-action ternperature-sensitiveelectrical switch, and more particularly to such a switch in which aspring-loaded member is released for movement by the melting of atemperaturesensitive pellet.

The present application is a continuation of my copending applicationSerial No. 35,557 filed June 13, 1960, and subsequently abandoned.

Temperature-sensitive compounds in various forms are used for electricalcontrol purposes. In some electrical switching devices a pellet oftemperature sensitive material is placed in confinement so that themelting of the pellet at the critical control temperature permits aspringbiased member to move to accomplish a switching action. In priordevices of this kind the direction of movement of the movable member hasbeen along the axis of confinement of the pellet.

One object of the present invention is to provide a device of the abovetype in which the spring-biased memher is released for movement at aright angle to the axis of confinement of the pellet.

Another object of the invention is to provide a tem-' perature-sensitiveswitch having a single set of parts which with normally-closed device ora normally-open device.

A further object of the invention is to provide a temperature-sensitiveswitch which is cheap and easy to manufacture and has high reliability.

The above and other objects and advantages of the invention will be morereadily apparent from the following description considered inconjunction with the accompanying drawing, in which:

FIGURE 1 is a longitudinal cross-sectional view of the inventionarranged to provide a normally-closed switch;

FIGURE 2 is a longitudinal cross-sectional view of the inventionarranged to provide a normally-open switch; and

FIGURE 3 is a fragmentary transverse view taken on the line 3-3 ofFIGURE 2.

Referring now to the drawing it will be seen that the inventioncomprises an elongated housing containing a spring-biased switchingmember which is selectively released for longitudinal movement withinthe housing so as to accomplish a desired switching action. In one endof the housing there are provided a pair of electrical terminals adaptedto be connected to an external circuit and which, in conjunction withthe switching element, accomplish the desired switching action. Theother end of the housing contains a temperature-sensitive pellet and amechanism which, in response to the melting of thepellet, releases theswitching element for longitudinal movement within the housing.

Referring now more specifically to FIGURE 1, a metallic switch housing Ahas a substantially cylindrical configuration. An insulating header E issuspended within one end of the switch housing A and is retainedsecurely in place by an in-turned end flange 11 of the metal housing.- Aspaced pair of electrical terminals C project longitudinally inwardlyfrom the header B, being also fanned slight modification may provideeither a rates Eatent slightly outwardly in a somewhat V-shapedconfiguration. Terminals C are the ends of conductors 18 which outsidethe housing A, may be connected to an external electrical circuit.

I A cylindrical insulating lining D extends throughout most of theinterior length of housing A, and has one end 13 in secure engagementwith header B so that terminals C are safely insulated from the housingA. A switching element or plunger E is positioned approximately in thelongitudinal center of housing A and adapted for longitudinal slidingmovement within the liner D. Plunger E has a wedge-shaped nose 15 whichis adapted to concurrently engage the inwardly facing surfaces of bothof the terminals C. Plunger E is made of an insulating material, andboth the liner D and plunger E may be made of Bakelite or similarmaterial.

Except for its nose 15 which is in the form of a fiat wedge (see FIGURE3) the plunger E is symmetrical about its longitudinal axis. Arelatively large concen tric bore in is formed in the rearward end ofplunger E. An aligned pair of small radial bores, not shown, are formedthrough the outer shell of plunger E on opposite sides of the bore 16. Aplunger pin F slidably retained in the aligned pair of small boresextends transversely through the large bore 16 of plunger E. A helicalspring G whose inner diameter is larger than the diameter of bore 16 ofthe plunger E is concentrically disposed within liner D on the rearwardside of plunger E. A spring retainer member H having an approximatelyV-shaped configuration has its apex disposed within the bore 16 ofplunger E and extending around the pin F so as to be supported thereby.The oppositely disposed legs 21, 22 of member H extend through spring Gand substantially rearwardly thereof.

A metallic pellet housing I is disposed within the other end of switchhousing A and engages the other end 14 of insulating liner D forretaining the latter in place. The corresponding end of switch housing Ahas an outwardly turned flange 12 which merges into a short longitudinalsection 26 of the housing A that is of somewhat larger diameter than themain portion of the switch housing. On the rearward end of longitudinalsection 26 there is formed an inwardly turned flange 27 which isparallel to and substantially coterminous with the flange 12.

The pellet housing I is symmetrical about its longitudinal axis, and hasa hollow interior providing a pellet chamber 30. On its forward end,which is in contact with one end of the spring G, the pellet housing Ihas formed therein an opening 31 whose diameter is somewhat less thanthe internal diameter of the spring G. Immediately to the rear ofopening 31 there is formed a sloped circumferential shoulder 32 whichfaces away from the opening 31. Chamber 30 then extends at constantdiameter throughout the greater part of the length of the pellet housingI, toward the rearward end thereof where a larger sloped circumferentialshoulder 33 is formed. Shoulder 33 also faces away from the opening 31.

Spring retainer member H consists of a thin flat metal strip or strapwhich, after being formed to its approximately V-shaped configuration,retains a considerable degree of resilience. Each leg 21, 22 of member Hhas a first oiiset portion 23 which conforms to the shape of slopedshoulder 32, as well as a second offset portion 24 which conforms to theshape of shoulder 33.

A temperature-sensitive peliet E has the form of a solid cylinder.Pellet I occupies pellet chamber 38, in engagement with the innersurfaces of both tainer member H between the first offset portions 23second offset portions 24 thereof. The diameter of pellet I is such asto force the retainer member legs tightly against the wall of pelletchamber legs of spring re- An outwardly extending circumferential ilange35 formed on the rearward end of pellet housing I engage the flange 12of switch housing A. A fiat circular metal base place K has acircumferential portion of its forward surface in engagement with thecircumferential surface of the rear end, including flange 35, of thepellet housing I. The center portion of the forward surface of baseplace K engages one flat end surface of pellet I, the other flat endsurface of pellet J being m inly open to the opening 31 of the pellethousing, but having its outer circumferential edge retained by shoulder32 of pellet housing 1 and offset portions 23 of the legs of member H.On its rearward circumferential edge the base plate K is retained withinthe flange 27 of switch housing A.

The invention is assembled as follows. The insulating header B is formedaround the spaced conductors 1% which provide terminals C. Header B isthen attached to the end of metal switch housing A in retainingengagement with flange 11 thereof. Insulating liner D is slidablyinserted within the housing A.

A sub-assembly is then prepared as follows. Spring retainer strap H ispositioned with its legs inserted within pellet housing I. Pellet I isinserted for retaining member H in place. Spring G is placed on theforward end of pellet housing I, concentrically surrounding the apex andother projecting portions of member H. Plunger E is placed in front ofthe forward end of spring G, and plunger E and pellet housing I arecompressed together so that the apex of the member H enters the bore '16of plunger E. Pin F is then transversely inserted through the smallbores in plunger E so as to retain the apex of member H.

The entire sub-assembly consisting of pellet housing I, pellet 1, memberH, spring G, plunger E, and pin F, is then inserted in a forwarddirection into the rear end of switch housing A. Thereafter, base plateK is placed in position, and flange 27 (previously left straight) iscrimped over so as to securely retain it.

The operation of the invention is as follows. A source of heat, which isto be used for temperature control purposes, is placed in conductiveengagement with the base plate K. Heat from the heat source flowsthrough base plate K into pellet l, and when its critical temperature isreached the pellet I suddenly melts. Since each oifset portion of memberH is hooked over the corresponding shoulder of pellet housing I, theeffect of the sloped configuration of both parts is to provide a camaction. Thus, when pellet J melts, the forward thrust of spring G uponplunger E, and hence upon the apex of member H, forces the leg ends ofmember H to move radially inward within the pellet housing I. The legends are therefore no longer longitudinally retained by the pellethousing, plunger E is no longer restrained by member H, and is forced byspring G to move longitudinally within liner D so as to engage theterminals C.

In FIGURE 1 a jumper wire L provides a transverse connection between theterminals C. Jumper wire L is relatively weak and hence frangible, andwhen plunger E moves forward the nose 15 thereof breaks the wire L andconsequently interrupts the circuit between conductors 1%.

The normally-open switch of FIGURE 2 is identical to the normally-closedswitch of FIGURE 1, except in two respects. First, the jumper wire L isomitted, and the circuit is normally-open. Secondly, the nose 15 ofplunger E is electro-plated with a conductive coating M. When nose 15 ofthe plunger E interengages terminals C the metal coating M provides acontinuous circuit therebetween.

The invention has been described in considerable detail in order tocomply with the patent laws by providing a full public disclosure of atleast one of its forms. However, such detailed description is notintended in any way to limit the broad features or principles of theinvention, or the scope of patent monopoly to be granted.

What I claim is:

1. A single-action temperature-sensitive electrical switch comprising:

an elongated housing having a transversely spaced pair of electricalterminals in the interior of one end thereof; a plunger in themid-portion of said housing adapted to slide toward said terminals forproducing an electrical switching action; means within the other end ofsaid housing providing a pellet chamber having an opening facing towardsaid plunger, and having an interior shoulder facing away from saidopening; a spring biasing said plunger for movement toward saidterminals; a resilient spring retaining member having one end fastenedto said plunger, its other end extending through said opening into saidpellet chamber and having an offset portion which hooks over saidshoulder; a temperature-sensitive pellet occupying said pellet chamberand compressively engaged by said spring retaining member formaintaining'the engagement of said offset portion of said member withsaid shoulder; and means for applying heat to said pellet from theexterior of said housing to melt said pellet, said offset portion ofsaid member and said shoulder together then providing a cam action forforcing said other end of said member radially inwardly of said chamberas said plunger moves toward said terminals.

2. A switch as claimed in claim 1 in which both said pellet chambershoulder and said offset portion of said member are sloped in adirection along the length of said housing.

3. A switch as claimed in claim 2 in which said member has a pair ofoppositely disposed legs positioned on respective sides or" said pellet,each of said legs has an offset portion, and said sloped shoulderextends circumferentially around said pellet chamber and is engaged bythe offset portion of each of said legs.

4. A switch as claimed in claim 1 in which said lastnamed means is allat circular metallic base plate which closes said other end of saidhousing, and said pellet has a fiat surface in flush engagement with theinner flat surface of said base plate.

5. In a temperature-sensitive electrical switch, the combinationcomprising:

housing means providing'a pellet chamber having an opening at one endand an interior shoulder facing away from said opening; an elongatedresilient plunger retaining member extending through said opening intosaid chamber and having an offset portion which hooks over saidshoulder; spring means biasing said member for longitudinal movementaway from said chamber, said shoulder and said offset portion being "ofsuch configuration as to cooperatively provide a cam action for forcingsaid offset portion in response to longitudinal movement of said memberto move transversely inwardly of said chamher; and a compressivelystressed temperature-sensitive pellet occupying said chamber andmaintaining said offset portion of said member in engagement with saidshoulder for inhibiting longitudinal movement of said member until theapplication of heat causes said pellet to melt.

' 6. A switch as claimed in claim 5 in which both said pellet chambershoulder and said offset portion of said member are sloped in adirection along the length of said member.

7. A single-action temperature-sensitive electrical switch comprising:

an elongated substantially cylindrical housing;

an insulating header secured in one end of said housing and carrying aspaced pair of electrical terminals adapted for external circuitconnection and which extend within said housing;

a plunger disposed in the longitudinal mid-portion of said housing andadapted to slide toward said terminals for producing an electricalswitching action;

means within the other end of said housing providing a pellet chamberhaving an end opening facing toward said plunger, said pellet chamberhaving first and second longitudinally separated and longitudinallysloping circumferential shoulders which face away from said end opening;

a compressed helical spring disposed on the pellet chamber side of saidplunger;

an approximately ti-shaped metal strap having the apex thereof fastenedto said plunger with its two legs extending through said spring andthrough said end opening into said pellet chamber, each of said straplegs having a longitudinally separated pair of sloping offset portionswhich conform to said pellet chamber shoulders;

a solid cylindrical temperature-sensitive pellet occupying said pelletchamber in relatively tight engagement with the longitudinal portions ofsaid strap legs lying between the ofiset portions thereof;

and means for applying heat from the exterior of said housing so as tomelt said pellet.

8. A single-action temperature sensitive electrical switch comprising:

an elongatedcylindrical housing having a transversely spaced pair ofelectrical terminals in the interior of one end thereof;

a frangible wire extending transversely between said terminals;

a plunger disposed within the mid-portion of said housing, said plungerbeing selectively slidahle toward said terminals and the forward endthereof being adapted to sever said frangible wire for interrupting theelectrical circuit between said terminals;

a cylindrical skirt disposed within the other end of said housing andforming an annular shoulder facing toward said plunger;

a helical compression spring having 'one end thereof in engagement withsaid annular shoulder and the other end thereof in engagement with therearward end of said plunger, and adapted to bias said plunger towardsaid terminals;

the interior of said cylindrical skirt having a smalldiameter portionadjacent said annular shoulder, a medium-diameter portion in itsmid-section, and a large-diameter portion at the extremity of said otherend of said housing, said cylindrical skirt also having first and secondcircumferential shoulders at respective ends of said medium-diameterportion, both of which are longitudinally sloped;

an approximately V-shaped metal retaining strap having the apex thereoffastened to said plunger with its two legs extending through said springand into opposite sides of the interior of said cylindrical skirt, eachof said retaining strap legs having a longitudinally separated pair ofsloping offset portions which conform to and normally engage respectiveones of said first and second circumferential shoulders;

a solid cylindrical temperature-sensitive pellet occupying saidmedium-diameter portion of said cylindrical skirt interior in relativelytight engagement with the longitudinal portions of said retaining straplegs lying etween the oifset portions thereof, and normally maintainedin compression thereby;

and means for applying heat through said other end of said housing tosaid pellet;

the action being such that when said pellet reaches its melting pointand commences to flow out of said medium-diameter portion of saidcylindrical skirt interior, the restraining force imposed upon said fouroifset portions of said retaining strap legs is no longer sufiicient toovercome said spring, and said strap legs move radially inwardly intothe space formerly ocupied by said pellet as said spring forcibly drivessaid plunger into contact with said terminals.

References Cited in the file of this patent UNITED STATES PATENTS630,671 Des Isles Aug. 8, 1899 748,240 Wall Dec. 29, 1903 1,875,928Lovekin Sept. 6, 1932 1,910,944 Austin May 23, 1933 2,159,423 BussmannMay 23, 1939 2,934,622 Massar Apr. 26, 1960 2,934,625 Patrichi Apr. 26,1960 2,934,628 Massar et al Apr. 26, 1960

1. A SINGLE-ACTION TEMPERATURE-SENSITIVE ELECTRICAL SWITCH COMPRISING:AN ELONGATED HOUSING HAVING A TRANSVERSELY SPACED PAIR OF ELECTRICALTERMINALS IN THE INTERIOR OF ONE END THEREOF; A PLUNGER IN THEMID-PORTION OF SAID HOUSING ADAPTED TO SLIDE TOWARD SAID TERMINALS FORPRODUCING AN ELECTRICAL SWITCHING ACTION; MEANS WITHIN THE OTHER END OFSAID HOUSING PROVIDING A PELLET CHAMBER HAVING AN OPENING FACING TOWARDSAID PLUNGER, AND HAVING AN INTERIOR SHOULDER FACING AWAY FROM SAIDOPENING; A SPRING BIASING SAID PLUNGER FOR MOVEMENT TOWARD SAIDTERMINALS; A RESILIENT SPRING RETAINING MEMBER HAVING ONE END FASTENEDTO SAID PLUNGER, ITS OTHER END EXTENDING THROUGH SAID OPENING INTO SAIDPELLET CHAMBER AND HAVING AN OFFSET PORTION WHICH HOOKS OVER SAIDSHOULDER; A TEMPERATURE-SENSITIVE PELLET OCCUPYING SAID PELLET CHAMBERAND COMPRESSIVELY ENGAGED BY SAID SPRING RETAINING MEMBER FORMAINTAINING THE ENGAGEMENT OF SAID OFFSET PORTION OF SAID MEMBER WITHSAID SHOULDER; AND MEANS FOR APPLYING HEAT TO SAID PELLET FROM THEEXTERIOR OF SAID HOUSING TO MELT SAID PELLET, SAID OFFSET PORTION OFSAID MEMBER AND SAID SHOULDER TOGETHER THEN PROVIDING A CAM ACTION FORFORCING SAID OTHER END OF SAID MEMBER RADIALLY INWARDLY OF SAID CHAMBERAS SAID PLUNGER MOVES TOWARD SAID TERMINALS.